📚 Year 7 WJEC Economics: Quick Reference Handbook for Formulas & Theorems | 七年级 WJEC 经济：公式定理速查手册
Welcome to your handy quick reference guide for Year 7 WJEC Economics. This handbook covers the essential definitions, formulas and theorems you will meet in your first year of studying economics. Use it to review key ideas before a test, complete homework tasks or simply build a solid foundation for the subject. Each topic is broken down into simple, memorable points with clear examples. Keep this guide close as you explore how people make choices, how markets work and what drives economic decisions.
欢迎使用这本七年级 WJEC 经济速查手册。本手册涵盖了你学习经济学的第一年会接触到的基本定义、公式和定理。你可以用它来考前复习、完成家庭作业，或者为这门学科打下牢固的基础。每一节都分解为简单易记的要点，并配有清晰的例子。当你探索人们如何做出选择、市场如何运行以及驱动经济决策的因素时，请把这本手册放在手边。
1. Scarcity and Choice | 稀缺性与选择
Scarcity means that there are limited resources to satisfy unlimited human wants. Because we cannot have everything we desire, we must make choices about how to allocate what is available. This fundamental economic problem affects every society, household and individual.
稀缺性是指有限的资源无法满足人类无限的欲望。由于我们不可能拥有想要的一切，我们就必须就如何分配现有资源做出选择。这个基本的经济问题影响着每一个社会、家庭和个人。
The concept of scarcity leads directly to the need for decision-making. Every time we choose one option, we give up another. The resources we use – land, labour, capital and enterprise – are all scarce in some way, which is why economists study how to use them most effectively.
稀缺性的概念直接导致了决策的必要性。每当我们选择一个选项，就会放弃另一个。我们所使用的资源——土地、劳动、资本和企业家才能——在某种程度上都是稀缺的，这就是经济学家研究如何最有效地使用它们的原因。
- Free goods vs. economic goods: A free good (like air) is abundant and has no opportunity cost, whereas an economic good is scarce and involves a cost to obtain.
- 免费物品与经济物品：免费物品（如空气）取之不尽，没有机会成本；而经济物品是稀缺的，需要付出代价才能获得。
- Needs vs. wants: Needs are essential for survival (food, shelter), while wants are desires that improve our quality of life (games, fashion).
- 需要与欲望：需要是生存所必需的（食物、住所），欲望则是提高生活质量的需求（游戏、时尚）。
Scarcity → Choice → Opportunity Cost
稀缺性 → 选择 → 机会成本
2. Opportunity Cost | 机会成本
Opportunity cost is the value of the next best alternative that is given up when a choice is made. In other words, it is not just the money you spend, but what you could have done with the time, effort or resources instead. Every decision has an opportunity cost.
机会成本是做出一个选择时所放弃的次优选项的价值。换句话说，它不仅仅是你花掉的钱，还包括你本可以用这些时间、精力或资源去做的事情。每一个决策都有机会成本。
When a government decides to build a new hospital, the opportunity cost might be the schools or roads that could have been built with the same budget. For a student, choosing to study for an extra hour means giving up one hour of leisure or sport. The formula is simply to identify the best forgone alternative.
当政府决定建造一所新医院时，机会成本可能是用同样预算本可以建造的学校或道路。对于学生来说，选择多学习一个小时就意味着放弃一个小时的休闲或运动。公式很简单，就是找出所放弃的最佳替代选项。
- Opportunity cost formula (verbal): Opportunity Cost = Value of Next Best Alternative Sacrificed
- 机会成本公式（文字描述）：机会成本 = 所放弃的次优选项的价值
- Practical example: If you have $10 and choose a book instead of a t-shirt, the opportunity cost is the enjoyment you would have gained from the t-shirt.
- 实际例子：如果你有10英镑，选择买一本书而不是一件T恤，机会成本就是你本可以从那件T恤中获得的满足感。
Opportunity Cost = Forgone Benefit of Next Best Choice
机会成本 = 次优选择的放弃收益
3. Factors of Production | 生产要素
The four factors of production are the resources used to create goods and services. They are commonly remembered by the acronym CELL: Capital, Enterprise, Land and Labour. Each factor earns a corresponding income: capital earns interest, enterprise earns profit, land earns rent and labour earns wages.
四种生产要素是用于创造商品和服务的资源。通常用首字母记忆：资本（Capital）、企业家才能（Enterprise）、土地（Land）、劳动（Labour）。每种要素获得相应的收入：资本获得利息，企业家才能获得利润，土地获得地租，劳动获得工资。
| Factor | Meaning | Payment |
|---|---|---|
| Land | Natural resources like soil, water, minerals | Rent |
| Labour | Human effort, both physical and mental | Wages |
| Capital | Man-made goods used in production (machinery, tools) | Interest |
| Enterprise | The ability to organise the other factors and take risks | Profit |
中文对照：
| 要素 | 含义 | 报酬 |
|---|---|---|
| 土地 | 自然资源，如土壤、水、矿产 | 地租 |
| 劳动 | 人类体力与脑力的付出 | 工资 |
| 资本 | 用于生产的人造物品（机器、工具） | 利息 |
| 企业家才能 | 组织其他要素并承担风险的能力 | 利润 |
4. The Production Possibility Frontier (PPF) | 生产可能性边界
The Production Possibility Frontier (PPF) is a curve that shows the maximum possible combinations of two goods or services that an economy can produce when all resources are fully and efficiently employed. Points on the curve represent efficiency, while points inside the curve show unemployed resources, and points outside are unattainable with current resources.
生产可能性边界（PPF）是一条曲线，表示当一个经济体的全部资源得到充分且有效的利用时，所能生产的两种商品或服务的最大可能组合。曲线上的点代表有效率，曲线内的点表示资源未充分利用，曲线外的点在当前资源下无法达到。
Movement along the PPF illustrates the concept of opportunity cost: to produce more of one product, we must sacrifice some of the other. The curve is usually bowed outward, reflecting increasing opportunity costs as we reallocate resources that are not equally suited to both goods.
沿着PPF移动说明了机会成本的概念：要多生产一种产品，就必须牺牲一些另一种产品。曲线通常向外弯曲，反映出当我们重新配置并不完全适合两种产品的资源时，机会成本会递增。
- Efficient point: Any point on the PPF line – e.g., producing 50 units of food and 30 units of clothing.
- 有效率点：PPF线上的任何一点——例如，生产50单位食品和30单位服装。
- Inefficient point: A point inside the curve, where resources are idle or underused.
- 无效率点：曲线内部的点，资源闲置或利用不足。
- Economic growth: An outward shift of the PPF caused by more resources or better technology.
- 经济增长：PPF向外移动，由更多资源或技术进步引起。
5. Specialisation and the Division of Labour | 专业化与劳动分工
Specialisation occurs when individuals, firms or countries concentrate on producing a narrow range of goods or services. The division of labour breaks down a production process into small, repetitive tasks performed by different workers. Both concepts increase productivity, meaning more output can be produced with the same input of resources.
专业化是指个人、企业或国家集中生产少数几种商品或服务。劳动分工则是将生产过程分解为不同工人完成的细小、重复的任务。两者都能提高生产率，即用同样的资源投入生产出更多的产出。
Adam Smith described how a pin factory divided the work into 18 separate operations, enabling workers to produce thousands of pins a day rather than just a few. The advantages include time-saving, skill improvement and the ability to use specialised machinery. However, work can become boring, and interdependence increases.
亚当·斯密曾描述一家别针工厂如何将工作分成18道独立工序，使工人每天能够生产成千上万根别针，而不只是几根。其优点包括节省时间、提高技能和能够使用专用机械。但工作会变得枯燥，相互依赖性也会增强。
- Benefits of specialisation: Higher productivity, lower unit costs, better quality, efficient use of talents.
- 专业化的好处：更高的生产率、更低的单位成本、更好的质量、有效利用人才。
- Disadvantages: Repetitive jobs can reduce motivation, and if one part of the chain fails, the whole process suffers.
- 缺点：重复性工作会降低积极性，如果链条中的一个环节出了问题，整个流程都会受影响。
6. Demand: The Law of Demand | 需求：需求定律
Demand refers to the quantity of a good or service that consumers are willing and able to buy at different prices over a specific period. The law of demand states that, all else being equal, as the price of a product rises, the quantity demanded falls, and vice versa. This inverse relationship is shown by a downward-sloping demand curve.
需求是指消费者在一定时期内，在不同价格水平下愿意并且能够购买的商品或服务的数量。需求定律指出，在其他条件不变的情况下，当一种商品的价格上升时，需求量会下降，反之亦然。这种反向关系表现为一条向下倾斜的需求曲线。
A change in price causes a movement along the demand curve (called a change in quantity demanded). Factors that shift the entire demand curve include changes in income, tastes, the prices of related goods (substitutes and complements), advertising and population size.
价格变化导致沿着需求曲线的移动（称为需求量的变动）。导致整条需求曲线移动的因素包括收入变化、品味变化、相关商品（替代品和互补品）的价格变化、广告和人口规模。
- Substitute goods: If the price of tea rises, demand for coffee (a substitute) may increase.
- 替代品：如果茶的价格上涨，对咖啡（替代品）的需求可能会增加。
- Complementary goods: If the price of printers falls, demand for ink cartridges (a complement) may rise.
- 互补品：如果打印机的价格下降，对墨盒（互补品）的需求可能会上升。
Law of Demand: Price ↑ → Quantity Demanded ↓ (ceteris paribus)
需求定律：价格 ↑ → 需求量 ↓（其他条件不变）
7. Supply: The Law of Supply | 供给：供给定律
Supply is the quantity of a good or service that producers are willing and able to offer for sale at various prices over a given period. The law of supply states that, all else being equal, as the price of a product rises, the quantity supplied increases, and as price falls, quantity supplied decreases. This positive relationship creates an upward-sloping supply curve.
供给是指生产者在一定时期内，在各种可能的价格下愿意并且能够提供出售的商品或服务的数量。供给定律指出，在其他条件不变的情况下，价格上升，供给量增加；价格下降，供给量减少。这种正向关系形成了一条向上倾斜的供给曲线。
Producers are motivated by profit, so higher prices make it more attractive to produce and sell more. A change in price causes a movement along the supply curve, while shifts of the supply curve result from changes in production costs, technology, taxes or subsidies, the number of sellers and weather conditions for agricultural products.
生产者的动机是利润，因此更高的价格使生产和销售更多产品更有吸引力。价格变化导致供给曲线的移动，而供给曲线的整体移动则源于生产成本、技术、税收或补贴、卖者数量以及农产品的天气条件等因素的变化。
- Shift factor example: An improvement in technology reduces production costs, shifting the supply curve to the right.
- 移动因素示例：技术进步降低了生产成本，使供给曲线向右移动。
- Shift factor example: A new tax on a product increases costs and shifts supply to the left.
- 移动因素示例：对产品征收新税会增加成本，使供给曲线向左移动。
Law of Supply: Price ↑ → Quantity Supplied ↑ (ceteris paribus)
供给定律：价格 ↑ → 供给量 ↑（其他条件不变）
8. Market Equilibrium | 市场均衡
Market equilibrium occurs at the price where the quantity demanded by consumers equals the quantity supplied by producers. At this point, there is no excess demand (shortage) or excess supply (surplus). The equilibrium price is often called the market-clearing price because all goods offered for sale are bought.
当消费者需求量等于生产者供给量时的价格水平，就是市场均衡。在这一点上，不存在超额需求（短缺）或超额供给（过剩）。均衡价格常被称为市场出清价格，因为所有待售商品都被买走了。
If the market price is above equilibrium, a surplus exists, and sellers will lower prices to clear stock. If the price is below equilibrium, a shortage occurs, and buyers compete, pushing the price up. These forces push the market back to equilibrium without external intervention.
如果市场价格高于均衡水平，就会出现过剩，卖家会降低价格来清理库存。如果价格低于均衡水平，就会出现短缺，买家竞争会推高价格。在没有外部干预的情况下，这些力量会把市场推回均衡。
| Condition | Result |
|---|---|
| Price above equilibrium | Surplus → Price tends to fall |
| Price below equilibrium | Shortage → Price tends to rise |
中文对照：
| 状况 | 结果 |
|---|---|
| 价格高于均衡 | 过剩 → 价格趋于下跌 |
| 价格低于均衡 | 短缺 → 价格趋于上涨 |
9. Price Elasticity of Demand (PED) – Introductory Concept | 需求的价格弹性（入门概念）
Price elasticity of demand measures how responsive the quantity demanded is to a change in price. At Year 7 level, we focus on the simple idea: if a small price change causes a huge change in quantity demanded, demand is elastic. If a large price change causes only a small change in quantity demanded, demand is inelastic.
需求的价格弹性衡量需求量对价格变化的反应程度。在七年级阶段，我们关注简单的思路：如果价格的微小变化引起需求量的大幅变化，需求就是有弹性的；如果价格的较大变化只引起需求量的微小变化，需求就是缺乏弹性的。
Goods with many substitutes (like soft drinks) tend to have elastic demand because consumers can easily switch. Necessities (like water) have inelastic demand because people need them regardless of price. The formula for PED is expressed as a percentage change, but Year 7 students should first understand the basic responsiveness concept.
拥有许多替代品的商品（如软饮料）往往需求富有弹性，因为消费者可以轻松转换。必需品（如水）需求缺乏弹性，因为无论价格如何人们都需要它们。PED的公式用百分比变化表示，但七年级学生首先应理解基本的反应概念。
PED = % Change in Quantity Demanded ÷ % Change in Price
PED = 需求量的百分比变化 ÷ 价格的百分比变化
- Elastic demand (PED > 1): Quantity demanded changes more than proportionately; e.g., cinema tickets
- 富有弹性（PED > 1）：需求量的变化幅度大于价格变化幅度；例如电影票
- Inelastic demand (PED < 1): Quantity demanded changes less than proportionately; e.g., petrol
- 缺乏弹性（PED < 1）：需求量的变化幅度小于价格变化幅度；例如汽油
10. Markets and Economic Systems | 市场与经济体系
An economic system answers the three fundamental questions: what to produce, how to produce it, and for whom to produce. The main types are the free market economy, the planned (command) economy, and the mixed economy. Most real-world economies are mixed, combining elements of both market signals and government intervention.
一个经济体系回答三个基本问题：生产什么、如何生产以及为谁生产。主要类型有自由市场经济、计划（指令）经济和混合经济。大多数现实经济都是混合经济，结合了市场信号和政府干预的元素。
In a free market, decisions are made by individuals and firms through the price mechanism. Adam Smith referred to this as the 'invisible hand'. In a planned economy, the government owns resources and makes all production decisions. A mixed economy allows markets to operate in some sectors while the government steps in to provide public goods and address market failures.
在自由市场中，决策由个人和企业通过价格机制做出。亚当·斯密称之为"看不见的手"。在计划经济中，政府拥有资源并做出所有生产决策。混合经济允许市场在某些部门运作，而政府则介入提供公共物品并解决市场失灵问题。
- Market economy advantages: Consumer choice, efficiency, innovation.
- 市场经济的优点：消费者选择、效率、创新。
- Planned economy advantages: Can focus on equality and provide essential services for all.
- 计划经济的优点：可以注重平等，为所有人提供基本服务。
- Mixed economy: Both sectors coexist – e.g., the UK has private businesses and public healthcare.
- 混合经济：两个部门共存——例如，英国既有私人企业，也有公共医疗。
11. Money and Its Functions | 货币及其职能
Money is anything that is generally accepted as a medium of exchange. For an item to be considered money, it should fulfil four key functions: a medium of exchange, a store of value, a unit of account, and a standard for deferred payment. Without money, economies would have to rely on barter, which is inefficient.
货币是指被普遍接受作为交换媒介的任何东西。一样东西要被视为货币，应该履行四个关键职能：交换媒介、价值储藏、计价单位和延期支付标准。没有货币，经济体就不得不依赖物物交换，效率极低。
- Medium of exchange: Money allows us to trade without needing a double coincidence of wants.
- 交换媒介：货币使我们无需欲望的双重巧合就能进行交易。
- Store of value: Money can be saved and used later; though inflation can reduce its purchasing power.
- 价值储藏：货币可以被储存起来以后使用；但通货膨胀会降低其购买力。
- Unit of account: Money provides a common measure for pricing goods and keeping accounts.
- 计价单位：货币为商品定价和记账提供了统一尺度。
- Standard for deferred payment: Money is used for borrowing and lending; debts are expressed in monetary terms.
- 延期支付标准：货币用于借贷活动；债务以货币单位表示。
12. Budgets and Basic Cost-Benefit Thinking | 预算与基本成本收益思维
A budget is a financial plan that sets out expected income and expenditures over a period. Individuals, households, businesses and governments all use budgets to manage resources and avoid overspending. Balancing a budget involves making sure that total spending does not exceed total income; otherwise a deficit occurs.
预算是一份财务计划，列出了一段时期内预期的收入和支出。个人、家庭、企业和政府都使用预算来管理资源，避免超支。平衡预算意味着确保总支出不超过总收入；否则就会出现赤字。
Cost-benefit thinking is a simple decision-making tool: before making a choice, list the expected benefits and the expected costs, including the opportunity cost. If the benefits outweigh the costs, the decision is likely efficient. This approach helps explain why people and businesses make certain economic choices.
成本收益思维是一种简单的决策工具：在做选择之前，列出预期收益和预期成本，包括机会成本。如果收益大于成本，这项决策可能就是高效的。这种方法有助于解释为什么人们和企业会做出特定的经济选择。
- Budget surplus: Income > Expenditure
- 预算盈余：收入 > 支出
- Budget deficit: Expenditure > Income
- 预算赤字：支出 > 收入
- Balanced budget: Income = Expenditure
- 平衡预算：收入 = 支出
Net Benefit = Total Benefits - Total Costs (including opportunity cost)
净收益 = 总收益 - 总成本（包括机会成本）
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